Association of health behaviors, dietary habits, and oral health with weight gain after 20 years of age in community-dwelling Japanese individuals aged 40 years and older: a cross-sectional study

Objectives This cross-sectional study investigated the factors associated with weight gain ≥ 10 kg after 20 years of age in the general Japanese population, with a focus on the number of teeth. Materials and methods We included individuals aged ≥ 40 years from Yamagata prefecture, Japan from 2017–2021. A postal survey was conducted using a self-administered questionnaire; 5,940 participants were included in the final analysis. The questionnaire included items on lifestyle factors, medical history, physical and mental conditions, oral health, and dietary intake. A multivariate logistic regression analysis was used to identify independent associations between weight gain ≥ 10 kg after 20 years of age and various parameters; adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated. Results Less than 20 teeth, male sex, drinking habit frequency, eating very fast or fast, and a higher frequency of eating-away-from-home were significant factors associated with weight gain ≥ 10 kg after 20 years of age; individuals with < 20 versus > 20 teeth exhibited a 1.35-fold higher OR (95% CI 1.15–1.59; p < 0.01). Conclusions Our results suggest that having < 20 teeth may affect weight gain ≥ 10 kg after 20 years of age. However, owing to the cross-sectional study design, causality could not be determined. Therefore, maintaining healthy lifestyle behaviors to avoid tooth loss may also affect weight gain ≥ 10 kg after 20 years of age. Clinical relevance Having < 20 teeth has the potential to affect long-term weight gain after 20 years of age.